<HTML>
<HEAD>
<!-- This HTML file has been created by texi2html 1.45
     from schintro.txi on 19 Febuary 1997 -->

<TITLE>An Introduction to Scheme and its Implementation - Other Control-Flow Constructs</TITLE>
</HEAD>
<BODY>
Go to the <A HREF="schintro_1.html">first</A>, <A HREF="schintro_19.html">previous</A>, <A HREF="schintro_21.html">next</A>, <A HREF="schintro_143.html">last</A> section, <A HREF="schintro_toc.html">table of contents</A>.
<HR>


<H3><A NAME="SEC20" HREF="schintro_toc.html#SEC20">Some Other Control-Flow Constructs: <CODE>cond</CODE>, <CODE>and</CODE>, and <CODE>or</CODE></A></H3>

<P>
We've already seen that the special form <CODE>if</CODE> is a kind of expression,
which returns a value as well as affecting control flow.  Scheme also has 
<CODE>cond</CODE>, a more general conditional construct, and the extended
logical operators <CODE>and</CODE> and <CODE>or</CODE>.  These are all value-returning
expressions;  they're also special forms, not procedures: they control
<EM>whether</EM> expressions get evaluated, depending on the values returned by
other expressions.

</P>

<UL>
<LI><A HREF="schintro_21.html#SEC21">cond</A>: cond is like if...elseif...else if... else...
<LI><A HREF="schintro_22.html#SEC22">and and or</A>: and and or are "short-circuiting"
</UL>

<HR>
Go to the <A HREF="schintro_1.html">first</A>, <A HREF="schintro_19.html">previous</A>, <A HREF="schintro_21.html">next</A>, <A HREF="schintro_143.html">last</A> section, <A HREF="schintro_toc.html">table of contents</A>.
</BODY>
</HTML>
